Comment by vladvasiliu
3 years ago
> The out of memory behavior is also very bad on Linux, where it will just lock your system.
Don't modern distributions come with the OOM killer? On my Arch system I didn't have to do anything to have the one from systemd.
My anecdote is this:
I had a Ubuntu 20.04 VM from university with 64 GB memory and my process needed 70 GB and it did lock my system.
And the anecdote continues: I ran a 55 GB process on a 16 GB Mac and it finished without a problem and without me having to configure anything.
I don't think Ubuntu 20.04 is considered "modern" in this discussion, though macos did, at the time, already have ram compression.
Also, as a curiosity, do you know how much swap there was? Usually, distros only create a limited amount of it. But I agree, as a user, you shouldn't have to worry about that.
You’re comparing apples and oranges here.
Independently of the operating system , your 70g process might have an actual working set of 70 g, while the 55g might have had a working set of 1 gig.
Furthermore your Vm was running most likely in a shared environment, your swap partition running on shared not super fast io, etc - you may not even have had 64g of ram ( despite your Vm claiming the contrary ). Your Mac on the contrary, has what is says it has.
> swap partition
This is the difference. Linux has a swap partition. You fill up the dedicated swap partition (which you decide when you partition your drive and is unusable for anything else, so you want to keep it small) and boom you're out of memory, OOM starts killing random stuff.
macOS uses a dynamic swap file (technically its multiple files) on your boot drive that starts at 0 bytes that grows until your main partition runs out of space.
I wrote a small program to do some image processing, I had a memory leak that leaked uncompressed bitmaps, after a couple minutes browsing HN "why is that process so slow?", I go check, it turns out it had burned up like 200 GB of RAM on my 16 GB Mac without me even noticing. But it did actually complete without me bothering to fix the bug, so problem solved.
This also means macOS has a lot more leeway to, say, swap out background tabs you haven't touched in a week in favor of live data since it can grow that swapfile full of stale garbage.
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